Cardiac arrest - ARREST trial

The clinical question

In the UK there are over 30,000 out-of-hospital cardiac arrests (OHCA) a year, where the heart stops beating suddenly. Less than one in 10 people in the UK survive an OHCA. 

Currently, cardiac arrest patients are taken by emergency ambulance to the closest Accident and Emergency (A&E) department for treatment. But some evidence suggests that people may have a better chance of survival if they are taken straight to a specialist hospital, called a cardiac arrest centre. These centres have a team of doctors and nurses experienced in treating cardiac arrest, and facilities like on-site heart imaging services and cardiac intensive care. Often, a cardiac arrest is caused by a heart attack, and specialist centres also have catheterisation laboratories open 24 hours a day, 7 days a week, with the equipment and expertise needed to unblock an obstructed coronary artery causing a heart attack as soon as possible. 

It seemed intuitive that people who’ve had a cardiac arrest out of hospital would benefit from being taken directly to a cardiac arrest centre for treatment compared with A&E. The ARREST trial was funded by the BHF to find out if this was the case.

What did the study involve?

ARREST was conducted across 35 hospitals served by the London Ambulance Service from 2018 to 2022. Seven of these hospitals were cardiac arrest centres. The trial was paused twice during the COVID-19 pandemic (from March 2020 through to November 2020, and from January 2021 through to August 2021).

Adults who’d had a cardiac arrest out of hospital were judged as eligible for the trial if they had:

• no obvious non-cardiac cause of the cardiac arrest.
• no obvious signs on their ECG trace of the heart of a major STEMI heart attack — in the case of a STEMI heart attack, patients would automatically be transferred to a specialist centre for treatment. 

In total, 862 participants were recruited into the trial from across London. Patients were resuscitated by London Ambulance staff until their heart was beating again. They were then randomly assigned to one of two groups by the paramedic crew:

• Half the participants (431 patients) were transported to a cardiac arrest centre for treatment.
• The other half (431 patients) were transferred to the closest hospital emergency department in London.

If the nearest hospital emergency department was a cardiac arrest centre, then the patient was taken to the cardiac arrest centre as it was not deemed ethical to delay their trip to an emergency department for the sake of the trial. At the cardiac arrest centre or emergency department, treatment was left to the discretion of the doctors and the clinical team.

Participants were followed up for 3 months to record how many in each group had died. The trial team also recorded how well people could function at discharge from hospital and after 3 months, for example how good their memory was, if they were able to live independently, and their quality of life. 

What did the study show?

• The two trial groups were similar in terms of age (average age was 63 years), gender (a third were female) and the cause of their cardiac arrest.
• Overall, around 60% of people in the trial had a cardiac arrest because of a heart related condition. Around 20% had a non cardiac condition that led to an arrest, and the cause of cardiac arrest was not known in ~20% of participants. 
• Of the participants with a cardiac cause, around 40% had a cardiac arrest because of coronary heart disease, a third because of a heart rhythm disorder and around 18% had a heart muscle condition (cardiomyopathy).
• The same proportion of patients in each group (63% [258 people]) had died at 30 days after their cardiac arrest.
• There was also no difference between the two groups in death rates after 3 months.
• Functional status and quality of life were similar in both groups at discharge and at 3 months.  

Why is the study important?

Trials of out of hospital cardiac arrest are extremely difficult to conduct, so it’s a tribute to the investigators and London Ambulance Service that they managed to deliver the trial. They persisted with the trial despite the disruptions of the COVID-19 pandemic. To complete successfully, the ARREST team had to recruit patients 7 days a week, 24 hours a day. 

The expectation was that transfer to a cardiac arrest centre would improve the prognosis of patients, so the results of ARREST were surprising.  Dr Tiffany Patterson, ARREST clinical lead, proposed one explanation: 

However, he stressed that the trial had excluded patients who clearly had suffered a heart attack, and that this group of patients do benefit from going straight to a heart attack centre and having an attempt at reopening the coronary artery.

ARREST draws attention to the poor survival rate of OHCA, and the importance of bystander cardiopulmonary resuscitation (CPR) and early defibrillation. BHF has developed a free, online CPR training course, RevivR, to teach people how to perform CPR. The Circuit: The National Defibrillator Network is another BHF-led initiative that provides information about defibrillators across the UK so that ambulance services can quickly direct bystanders to their closest defibrillator in the crucial moments directly after a cardiac arrest.

Study details

“A randomised trial of expedited transfer to a cardiac arrest centre for non-ST elevation out of hospital cardiac arrest. The ARREST trial.”
Award reference: CS/16/3/32615
Principal Investigator: Professor Simon Redwood, King’s College London
Trial registration number: ISRCTN96585404

Publication details

Expedited transfer to a cardiac arrest centre for non-ST-elevation out-of-hospital cardiac arrest (ARREST): a UK prospective, multicentre, parallel, randomised clinical trial. Lancet. 2023;402 (10410):1329-37.